Use session to transmist username/ticket from fedeare view to login view

Hence, these parameter are not recorder in the user history, and thus
the user username do not apear anymore in the history. This respect more the
user privacy.

cas_server/federate.py

@@ -29,7 +29,6 @@ class CASFederateValidateUser(object):
                 service_url=service_url,
                 version=version,
                 server_url=server_url,
-                extra_login_params={"provider": provider},
                 renew=False,
             )